motorbicycle building

8/10/2019 Motorbicycle building

1/166

or

440

H68

ding


2/166

c

used

Whit

Emb

Boo

HON.

C

write

Forn

Tick.

Wo-

in.

inside

at the end. The diameter

of

the

prints

at the

other

two

ends

is

l

y

L

in. and

l-j

3

^-

in.

by

i

in.

long.

If

it

is decided

to

do with-

out

core-boxes

for

these two

patterns,

the

larger

part

will have to be

plain-cored

right through

l

T

3

^in.,

leaving

the recessed

portion

for

the

ball-

race

to be machined

out of

the

casting.

The

diameter

of

the

print

for the

lg-in.

tubes is the

same as

for

the

core-boxes,

but

the

length

is

differ-

ent.

The

core

being

supported

in

the

mould

at


27/166

PATTERNS FOR FRAME

CASTINGS.

25

one end

only,

the

print

must be

longer

on the

pattern

than

the

depth

to

be

cored. Thus the

pvint

for

the

top

head

lug

should

be

l\

in.

long,

//and

that

for the bottom

1|

in.

long.

//

Seat

Lug.

The seat

lug (Fig. 17)

is made

from

/

two

turned

parts;

the rear

part,

to

take

the

f-in.

bolt,

is

cut

out

by

hand,

similar in

shape

to

Fig.

18,

and

glued

and

pegged

on.

Turn

the

centre

part

for

the

down

tube 1

T

5

^

in.

in

diameter

in

the

centre,

tapering

to

1

-^

in.

at

each

end

by

If

in.

long,

the

print

standing

out

i

in. at

each

end

by

l

T

V-in.

in

diameter.

The

front

portion

for

the

top

tube

is

ly\-

in. in

diameter at

the

extreme

Fig.

19.

Lower

Horizontal

Lug.

edge,

tapering

up

at

about

3

degrees

of

taper.

The

core-print

for

this

member is

1

T\

in.

in

diameter

by

If

in.

long.

The

rear

part

is

cored out

f

in.,

as shown

by

the

dotted lines

in

Fig.

18,

and will

require

a

print

of

this

diameter,

standing

out

i

in.

at

each end.

Lower

Horizontal

Lugs.

The

patterns

for the

two

lower

horizontal

lugs

(Fig.

19)

are alike

except

in

the

angle,

the one

shown

being

69

de-

grees

and

the

other

57

degrees. They

are

made

from

two

turned

parts,

and

each member

is

to

take

lg-in.

tube.

The

parts

are

exactly

as

the

main

parts

of the

seat

lug,

the

only

difference


28/166

26

MOTOR

BICYCLE

BUILDING.

being

the

absence

of

the rear

ears

and

the

different

angle

of

the front

lug

that

is,

57

degrees.

The

same

remarks

apply

with

regard

to

the core-

prints.

Girder Tube

Lugs. Figs.

20 and 21

are

side

and

top

views

of one of

the

girder

tube

lugs.

A

pair

of

these

will

be

required,

but the

difference

is

so

slight

that one

pattern may

be used

for

both.

This

pattern

should

be

made

with

the

grain

of

the wood

running

with

the

length

of the

pattern,

and the

prints glued

and

pegged

on

each side.

The

drawings give

all

dimensions,

which are

Figs.

20 and 21.

Girder

Tube

Lujrs.

finished

sizes of the

machined

casting,

so

due

allowance

must

be

made for

machining.

The

core

and

print

for

the oval

part

should

be made as

near the finished size as

possible,

as

this

has to

be

filed out in

the

casting.

It

will

be

necessary

to

have

a core-box for the

oval

part

;

a

piece

of

fork

tube

of this size and section

will

answer

ad-

mirably.

The

length

of

prints

for

both

oval

and

round

holes need be

only

J

in. from each

side

of

the

pattern.

Front Fork

Crown.

The

pattern

for

the

front

fork crown is

shown

in

top

and

front view

by


29/166

PATTERNS

FOR

FRAME

CASTINGS.

27

Figs.

22

and 23. It

may

be made

from

one

piece,

with

the

prints

for the

central

core and

two oval

cores

glued

and

pegged

on.

It is

4f

in.

over

all,

If

in.

deep

at the

ends,

where the

forks

fit,

and

1^

in.

deep

in

the centre.

The

central

core-print

is l

T

Vin.

in

diameter,

and

the

ovals,

indicated

by

dotted

lines

in

Fig.

22,

Ij

in.

by

i

in.

;

that

is

the

full

finished

size,

and

owing

to

the awkward-

ness

of

cleaning

out

these

in

the

casting,

it

will

be

advisable

to

core them out

full

size,

or

very

Figs.

22 and

23. Front

Fork

Crown.

nearly

full size.

A

core-box

will

be

necessary

for

this

pattern,

allowing

for

a

uniform

thickness

of

-

in. in the

casting,

as shown

by

the

dotted

lines

in

Fig.

23, except

at

the

edges

of the

oval

open-

ings,

which

may

be a

bare

/

a

-

in. It

will be

noticed that

a

ring

or

collar

is

shown

on

top

of

the crown

;

this

is

for the

bottom ball-race

to

fit

on.

The

core-prints

need

only project

f

in.,

as

the

core

will

be

supported

at

four

points.

Ball-head

or

Steering

Tube

Lug.

The

ball-


30/166

28

MOTOR

BICYCLE

BUILDING.

head,

or

steering

tube

lug,

is

shown

by

Figs.

24

and

25,

these

being

side

and

bottom views.

It is

made

by

turning

the

main

part

to

the

dimensions

given,

allowing

for

machining.

The central core-

print

is

ly^in.,

projecting f

in. at each

end. The

rear

part

for

the

f-in.

bolt

is cut

out

separately,

and

glued

and

pegged

on.

It

is l

in.

wide,

and

has a

f-in.

core-print.

The

two

projections

to

Fig.

25.

Figs.

21

and

2o.

Steering

Tube

Lug.

receive

the

ends of

the

girder

tubes are cut out

to

shape

as

in

Fig. 25,

length

with

the

grain,

and

the two

lugs

turned

to

shape

and

glued

and

pegged

on.

The

prints

are

y

7

^

in.

in

diameter

by

f

in.

long.

The

two

projecting

pieces

being

so

light

(only

T

3

(T

in.

thick),

they

should

be dovetailed

into

the main

part

of

the

pattern,

as well as

glued

and

pegged,

or

they

may

soon

be broken off

at

the

foundry.


31/166

PATTERNS

FOR FRAME CASTINGS.

Engine

Plates.

The

pattern

for

the

engine

plates

is shown

by

Figs.

26

and

27,

which

are

side

and

end

views. Four of

these

plates

will

be

re-

quired.

They

may

be cast in malleable

iron

from

a

pattern,

but

it

is better

to

have

them

forged

from mild steel.

Should

castings,

however,

ba

used,

have

only

the

large

centre

hole

cored,

leav-

ing

the

ends

solid

to be

drilled

out in

the

casting.

Fig.

20.

Fig.

27.

Figs.

26

and

27.

Engine

Plate.

This

also

applies'

if

forgings

are

used,

as

the

exact

position

of.

these holes

can

only

be

ascer-

tained

when

the

frame

is

built

and

the

engine

tried

in

the

frame,

with

wheels in

position.

Leave

on

Patterns.

This

is

all

the

pattern-

making

that

will

be

necessary,

and

it

only

re-

mains to

get

the

required

number

of

castings

made

from

them

at a

good

malleable iron

foundry.

All

parts

of the

patterns

must

be

nicely

smoothed off


32/166

30

MOTOK BICYCLE BUILDING.

with

fine

glasspaper,

leaving

no

rough

edges

or

parts,

and

care

must

be

observed

to

impart

suffi-

cient

leave

to

the

various

parts

requiring

it.

What

is

meant

by

leave

on

a

pattern

will

be

understood

by

taking,

first,

a solid ball

and

then

a solid

square

as

patterns.

The ball would

be

moulded half

in

each

moulding

box,

the

parting

taking place

exactly

at the centre of the

pattern

;

thus,

as all

parts

of

this

pattern slope

away

from

the

centre

or

parting

line,

no

leave

would be

necessary,

as this

would

be

a

perfect

form for

leaving

the

sand

well.

But

if a solid

square

or

cube is

taken,

some

part

of

the

pattern

would

have to

be

tapered

off

to

enable the

pattern

to

come

away

from the sand

without

breaking

down

some

part

of

the

impression,

unless the

pattern

was

moulded

with

a

corner of the

square

upper-

most,

and the

parting

takes

place

at a

point

which

embraces four corners.

Whatever

other

position

this

pattern

might

be moulded

in,

some

portions

of

the

flat

sides

would

have

to

be

tapered

off from the

parting

line

to enable

it to

leave

properly.

It

is

only

necessary

to

look

at

a

pat-

tern

carefully

and

imagine

which will

be

the most

convenient

position

to mould

it

in,

to

see

what

parts

require

leave.

Painting

Core-prints,

etc.

All

core-prints

should

be

painted

black

a

little

vegetable

black mixed

with

varnish will

do

and

the

whole

pattern

given

two

coats

of

shellac

varnish. This

varnish can be

easily

made

by

dissolving

brown shellac

in

methylated

spirit, shaking

the bottle

frequently.

Heat

will

assist

it

to

dissolve,

but

great

care must be

taken,

as

the

spirit

is

very inflammable,

and

likely

to cause

an

accident

if

taken

too

near a

light.

The

inside

of

the core-boxes

should

also

be

given

two

good

coats

of shellac

varnish

when

finished.

Making

Plain

Round

Cores.

For

making

the


33/166

PATTEKNS FOR FRAME

CASTINGS.

31

plain

round

cores,

nothing

beats

cycle

tube,

and

pieces

of

this

to

fit

the

various

prints

should be

selected

and

cut

to

the

required

lengths.

Where

the

junction

of two

cores

is

at an

angle,

such

as

the head

lugs,

seat

lug,

and lower horizontal

tube

lugs,

the core tubes

should

be

cut

off at a cor-

responding

angle,

and also

hollowed out at the

angle

end,

so

that

the

coring

may

extend as

far

as

possible.

Oval Gores.

For

the

oval cores

also

pieces

of

fork

blade

of the

proper

section

will

do

perfectly

for

making

the

cores,

and

will

save

a

deal

of

trouble

in

core-box

making.

Dowelling

Halves

of

Gore-boxes. The

two

halves

of

the

core-boxes

for

fork

crowns,

or what-

ever core-boxes

that are

made

in halves,

should

be fitted with two

or

three

dowels

to

ensure

the

halves

closing perfectly

accurate

;

they

should fit

easily,

but

without shake.

Small brass

pegs

and

sockets can be

purchased

for

the

purpose,

and

where

the boxes

are

likely

to be

used much it

is

advisable

to fit

these,

as

the wood

dowels soon

wear

with

much

usage.

Metal

Patterns.

Where

a

large

number of

castings

are

to

be

made

from

one

pattern,

metal

patterns,

preferably brass,

are

made,

and

cast-

iron

core-boxes used.

Dimensions

on

Illustrations.

It

must

be

borne

in

mind that

all dimensions

given

in

the

illustra-

tions

included

in

this

chapter

are

finished

sizes

of

castings,

and

due

allowance

must be

made

for

machining.


34/166

CHAPTER

III.

BUILDING FRAME

FROM

CASTINGS.

HAVING

received

the

castings

from

the

foundry,

free them

well

from

sand

;

and should

any

castings

have

become

distorted in

the

annealing

process,

correct

this

by

careful

hammering.

Bottom Bracket. The bottom

bracket

may

first be

taken in

hand. Chuck

the

casting

in

a

jaw

chuck,

and bore

out

the

centre

part

ly

7

^

in. in

diameter, leaving

f

in.

at

each

end

a

full

\^

in.

to

screw

if

in.

by

24

threads.

Face off

the end

standing

out from

the

chuck

at

this

setting

;

the

other end

should

be

faced

off on a

screwed mandrel

to

get

perfect

truth

;

but

if

carefully

chucked,

it

may

be

faced

fairly

true

by

this

means.

The

bracket

cups

should

be

obtained

or

made

previous

to

screwing

the

bracket,

so

that

they

may

be

tried

in

to

fit

before

removing

the

casting

from

the

chuck.

The

cups

should be a

good

tight

fit,

so

that

they

can

only

just

be

screwed

up

with

a

peg

wrench. The width of

the

bracket when

finished

should

be

3^

in.

Boring

the

Three Tube

Lugs.

The best

way

to

bore the three

tube

lugs

will

be

on

an

angle

plate

or an

upright

drilling

machine

;

but if

such

a tool

is

not

available,

the

lathe

will

do,

either

by

bolt-

ing

the

angle

plate

to the

face

plate,

or

by

hold-

ing

the

casting

in the

jaw

chuck.

If

the

latter

method

is

adopted, greater

care

will

be

necessary

in

seeing

that

the

holes

are

bored

at

perfect

right

angles

to

the

centre bore. With

a

true

angle

plate

and

the

ends

of

the

casting

faced

true,

this

will

be

ensured.

The

front

member,

to take

the

tube

from

the

back

fork

crown,

will be

bored

If


35/166

BUILDING FRAME FROM

CARTINGS.

33

in.

right through

into

the

centre,

and the

outside

trued

up.

The

lug

to

take

the down

tube

will now

be

bored

Ij

in.

right

through,

and

at

an

angle

of

110

degrees

with

the

first

boring.

The

rear

lug

is

bored

If

in. at

an

angle

of

64

degrees

with

the

last

boring.

The various

tubes

should

be

tried

in

their

places

before

the

casting

is

shifted,

and

should be a

good tight

push

fit in

their

holes.

Holes

for

lubricators

should

be

drilled

f

in.

from

each

face,

in

such

a

position

that the

lubricators

will

be

upright

when

the bracket

is

in

position.

If

lugs

for

set

pins,

by

which

the

cups

or

discs

are

to be

locked,

have

been

provided,

these

should

be

drilled and

tapped

to

suit

the set

pins.

The

dimensions

of

the

disc to be used with

lock-nuts,

and

also

of

the

bracket

axle,

will

be

given

later.

Back Fork

Crown.

The back

fork

crown

cast-

ing

should

be

chucked

in

the

jaw

chuck and

bored

If

in.,

as

deep

as

possible,

and the

edges

trued

up

;

or

the

ends of the D-section

projections

may

be

levelled

off

and

the

casting stripped

to

the

face

plate

to bore this

If

in. hole.

Whichever

method

is

adopted,

care

must

be

taken

to

get

the

hole

perfectly

true

with

the

D

ends.

Engine Lugs.

The

engine lugs

should

be

chucked

true,

and

the

f-in.

holes bored

right

through

and

reamered,

the faces

being

turned

up

on

a mandrel.

They

should

measure

3^

in.

over

all when

finished.

The

tube

lugs

should

then be

bored

ij

in. and

If

in.

respectively,

and

the

edges

trued

up.

Front

Fork

Ends. The

castings

of

the

front

fork

ends

will

require very

little

machining.

The

f-iri.

hole

will

require

drilling,

and

the

f-in.

recess

should

be

machined

in

the

outside face of

each

with

a

peg

drill

or

cutter.

The

slot

can

then be

filed

out to

meet

the

f-in.

hole.

The

f-in.

lug

to

take

the

bottom

end

of

the

girder

tube

can

be

turned

or

filed as

preferred.

As

this

is a rather

awkward

casting

to

chuck,

it

may

be advisable

to

c


36/166

3i

MOTOR BICYCLE

BUILDING.

file

this

to

fit

the

tube at

the

same time

as

the

oval

lug

is

filed to fit

the

lower

end

of

the

oval

fork blade.

Whilst

these

are

being

fitted

to their

respective tubes, they

should be

tried

on

the

full-

size

drawing

to

see

that

the

angle

is correct. The

two

stay

eyes

will

require

drilling

out

f

in.

;

these

may

be

drilled

at

the

same

time

as

any

of the

other

|-in.

holes.

Head

Lugs.

Chuck

the head

-lugs

in

the

jaw

chuck, large

end outwards

;

bore

through

Ij

in.

to

fit

the

head

tube,

and

turn

out

the

recess

fo,r

ball-races,

as

shown

by

the dotted

lines

in

Figs.

15

and 16

(p. 23).

These

recesses

will

measure

^\

in.

at

the extreme

ends

by

^

in.

deep.

Face

off the

ends,

and true

up

the

outer

edges.

The

Ij-in.

tube

members

may

be bored

whilst

held

in

the

jaw

chuck

or

on

the

angle plate,

tilted

to

the

correct

angle

112

degrees

for

the

top

head

lug

and 56

degrees

for

the

bottom one.

Seat

Lug.

Chuck

the

seat-lug casting

in the

jaw

chuck

to bore

out the

central

lj-in.

hole,

with

the

top

end outwards

;

re-chuck

or fix

on

the

angle

plate,

to

bore

out the

Ij-in.

hole

for

the

front

tube.

The

rear

part

will have

to

be

drilled out

|

in.,

and

ths

ears

faced

off

true

for the

back-stay

eyes

to

bed

against.

The

saw-cut should

be

put

in

the

back,

midway

between

the

ears,

before

the

lug

is

fitted

and

brazed to

the

seat

tube,

as

the

casting

becomes

very

hard

and

difficult

to

saw

after it

has

been

brazed.

Lower

Horizontal Tube

Lugs.

The treatment

of

the

lower

horizontal

tube

lugs

is

the

same

as

that of

the

seat

lug

;

but

note

should

be

taken

of

the

difference

in the

angle.

Drilling

Girder Tube

Stays.

The

|-in.

hole

in

each of

the

girder

tube

stays

may

be

bored

on

the

drilling

machine or

the lathe. In

setting

these

castings

for

boring

the

|-in.

hole,

due

allowance

should

be

made

for

the

difference in

parallel

be-

tween this

and

the

oval

hole. On

reference

to

the


37/166

BUILDING

FRAME

FROM CASTINGS

35

full-size

drawing,

it will

be

noticed that

the

girder

tubes

approach

nearer

to

the

centre

steering

line

as

they

reach the

top

of the

head.

Also,

looking

from

the

front

of

the

machine,

it will be seen

that

the two

tubes

are closer

together

at

the

top

than

they

are

at

the fork crown.

If

this difference

is

allowed

for

when

drilling

the

f-in.

holes,

it will

not

be

necessary

to

bend the

tubes

to

bring

them

into

place.

Knocking

these

lugs

on

a

f-in.

man-

drel,

after

they

are

drilled

and the

edges

trued

up

in

the

lathe,

will

add

greatly

to

their

appearance.

The

oval holes must be filed out

to

fit

the fork

blades.

Front Fork

Crown.

The front fork crown

may

be

held

in

the

jaw

chuck or

strapped

to

the

face-

plate,

the

centre

hole

bored

1|- in.,

and

the

top

faced

off

and

the

shoulder turned

1^

in.

in

diameter

by

|

in.

deep.

If

the

casting

is

being

machined, strapped

to the

face-plate,

this latter

operation

will have- to be done on a

mandrel be-

tween the

centres.

The

oval-section

holes

will

have

to

be

filed

or

scraped

out

for

the

fork

blades

to fit.

While

the

casting

is

on

the mandrel in

the

lathe,

the

ends

of

the

ovals

may

be

faced

off

true.

Steering-tube

Lug Casting.

Chuck the steer-

ing-tube

lug casting

bottom or

large

end

outwards,

bore

through

lj

in. to

fit

the

steering

tube

(a

tight

hand

fit),

and

recess out

the

part

shown

dotted

in

Figs.

24

and

25

(p.

28)

to

take

the

ball-race.

This will

be of

the

same

size

across

as

the

recesses

in

the

head

lugs,

but

V

in.

deeper,

so

that

the

edge

of

the-

casting

may

overlap

the

outer

edge

of

the

top

ball

head

lug

when the two are

brought

together

with

the

balls

in

place.

This

hides

the

balls,

and

keeps

the

bearing

more

or

less

dust-

proof.

The

bottom

ball

head

lug

should

be

made

to

overlap

the

bottom

ball-race

on

the

fork

crown

in

the

same

manner

for

the same

purpose.

At

this

chucking,

the

under side of

the front

ears

may

be

faced,

as

well

as the

edges

of

the

two


38/166

36

MOTOR

BICYCLE

BUILDING.

girder

tube

lugs,

on

a

mandrel

in

the

lathe

centres

;

the

outside

and

top

of

the

casting

may

be

turned

up,

or as much

of

the

outside

as the

projections

will

allow.

The

ears

should

be drilled

out

|

in.,

and faced

on both

sides

with

a

facing

cutter

;

the cutter

that

was

used

for

recessing

the

front

fork

ends

will

do

for

this

also.

The

two

^-in.

holes

for the

girder

tubes

must now

be

drilled,

and

finished

out

with

a bottoming

drill

or

cutter,

so

that

the holes

have

square

corners or

a

flat

bottom.

A

fine

saw-cut

should be

made

nearly

half

through

the

casting, just

under

the

ears,

as shown

in

Fig.

24

(p.

28),

and a

broader

cut

should

be

run down to

meet this

midway

be-

tween

the ears.

Engine

Plates.

The

four

engine-plate castings

should

be

levelled,

the

|-in.

holes

drilled

square

with

the

face,

the sides

smoothed,

and the

edges

filed

up.

One

of the

|-in.

holes in

each

plate may

be

marked

off

and

drilled,

leaving

the other

|-in.

holes

to

be

marked

off and

drilled

after the

frame

is

built

up

and

the

engine

is in

position.

Ball-races.

It

will now

be

necessary

to

make

the

ball-races

(Figs.

28 and

29,

p.

37).

Four of

these will

be

required three,

as

illustrated,

for the

steering

tube

lug

and the

top

and bottom head

lugs,

and

one

for

the fork crown

;

this

last

will

have

square

corners instead

of

round,

and

a

lyV

in.

hole

to

fit

the

shoulder

on

the

fork

crown,

the

outside diameter

being

1^4

in.

These

are

rather

awkward

to

make

in

an

ordinary

lathe

;

to

get

them true

they

are

made

on a

large

hollow

mandrel

lathe

from the bar.

It would

be

as

well

to

buy

these

ready-made,

as

they

do

not

cost much. If

it

is

decided

to

make

them,

good

mild

steel,

well

case-hardened,

should

be

used.

It

would

be

simpler,

in

making

the

steering bearings,

to

dis-

pense

with

cups

or loose

ball-races

altogether,

and

turn

the

ball-races

in the head and

steering

lugs

themselves,

with a steel

cone

only

to

fit on

the

fork


39/166

BUILDING

FKAME FROM

CASTINGS. sf

crown.

In

this

case

the

bearings

should

be

two-

point

bearings,

and

not

four-point,

as

shown

with

the

loose

ball-races.

These

parts

will not

bo

so

durable

as

well-hardened

steel ball-races

;

but

if

balls

not

less

than

^'V

in.,

or

T

3

(I

in. for

the

top

bear-

ing

and

-^L

in.

for

the

bottom

bearing,

are

used,

they

will

wear

very

well.

The malleable-iron

castings

become

very

hard when

they

are

brazed,

and

thus

stand a

lot

of

wear.

The

loose

steel

cone on the head

will,

of

course,

be

well

hardened,

and

the

radius of

the

bearing

curves

should not

be much

greater

than the radius

of

the

ball

used,

thus

giving

a

good large

bearing

surface,

instead

of

the

small

bearing

surface

usual with

V-groove

Fig.

28.

Fig

29.

Figs.

28 and

29.

BalJ-race.

bearing

discs.

One

advantage

of

the

absence of

loose

ball-race

bearings

is

that there

are

no

separ-

ate

parts

to

gst

loose

and

cause

play

in

the

head

Bottom

Bracket

Axle.

Fig.

30

gives the

full

dimensions

for

the

bottom

bracket

axle,

which

should

be

made,

preferably,

from

one

of Lead-

beater

&;

Scott's

patent stampings.

These

have

a dead

soft

centre,

which

will not

harden,

with

an

exterior

covering

of

a

carbon

steel

that

will

harden

direct

in

water,

and

gives

a

very

hard

wearing

surface.

Failing

one

of

these-

stampings,

cast

steel

should be

used,

carefully

hardened at-

the

wearing

parts only.

Mild

steel,

case-hard-

ened,

does

very

well

for

this

job

if

proper

facilities,

are

at

hand

for

pot-hardening

;

but

using

mild


40/166

3S

MOTOR BICYCLE BUILDING.

steel,

and

attempting

to harden

by

the

ordinary

means on

the

open

hearth with

potash,

etc.,

is

quite

useless.

In

making

this

axle,

cut off

the

steel

or

stamping just

the

dead

lengths

required

before

drilling up

the

ends,

so that the centres

upon

which

the

axle

is

turned

may

be

left

in,

to true

it

up

by

after

hardening.

Fit

the cranks

and file

the

keyways

before

hardening.

Special

wide bracket

discs

are

used

with

this

axle,

as

shown

at

A,

lock-

nuts

(Figs.

31 and

32)

securing

them.

If it has

been decided to

lock

these

discs

by

set

pins

or

transverse

cotters,

the

ordinary

standard

pattern

discs,

which

can

be

purchased

for about

6d.

each,

will

do.

Should lock-nuts

for

the

bracket

discs

be

Fig.

30.

Bottom Bracket

Axle

in

Position.

necessary,

they

may

be

made

from

ordinary

gas

back-nuts,

bored

out and

re-screwed,

if suitable

stampings

are not

available

; or,

if

the latter are

used,

they

can be made

from

stout 1-in.

washers,

bored and screwed.

They

need not be filed

up

or

shaped hexagon ;

but a

couple

of

deep

notches

may

be

filed in their

edge

for

adjustment pur-

poses,

as

shown

in

Figs.

31

and

32.

They

should

be

If

in.

by

24

threads,

the

same

as

the

discs,

but

must

be

a

somewhat

easier

fit

on

the

discs

than

the

discs

are

in

the

bracket,

otherwise

diffi-

culty

will

be

experienced

in

adjusting

the

bearing

properly.

At

least

one face

of

the

nuts

must be

trued

up

with

the thread.

Fitting

Lock-nut

to

Steering

Tube.

The

steer-


41/166

BUILDING FRAME FROM

CASTINGS. 39

ing

tube

must be screwed

at one

end

with a fine

thread for

|

in. down. A

coarser thread

than

26

to

the

inch should

not

be

used,

otherwise

the tube

would

be

weakened

by

the

depth

of

the

thread.

A

lock-nut

to fit

this

will

be

required,

and

the

re-

marks made

with

reference

to

the bracket lock-

nuts

applj

7

also

to this.

Whilst

screwing

the

steer-

ing

tube

and

fitting

the

nut,

pay

attention

to

the

fitting

of

the

steering-tube

lug,

which

must

be

a

good

sliding

fit

without

shake.

The

saw-cut,

which allows

the- tube

to

be

tightened

on

to

the

Fig-.

32.

Figs.

31

and

32.

Bracket Lock-nut,

handle-bar

stem,

should

not

be

made

until

the

handle-bar

has

been

fitted

in

the

tube.

Engine

Bolts. Two

f-in.

turned

engine

bolts

(Fig.

33)

will be

required

for

securing

the

engine

plates

to their

lugs.

These

are turned from

li-in.

mild

steel,

one to the

dimensions

given

in

the

illustration,

and

the

other

\

in.

shorter.

They

should

be

a,

good push

fit,

without

shake,

in the

f-in.

holes

of

the

engine

plates

and

the

lugs

on the

frame.

Building up

Frame.

All

the

lugs

and

parts

having

been machined

ready

for

fitting

up

to

the

various

tubes,

the

rear

part

of

the frame

may

now

be

built

up.

Cut

off

the

back

forks

to

the


42/166

40

MOTOR

BICYCLE

BUILDING.

exact

length

required

;

clean out

the ends

where

the fork ends

and

fork crown

ends

fit

;

level

off

the

ends

where

the

fork

ends

fit

;

and

chamfer

off

the

inner

edge

of

the

D

tubes,

so

that

they

fit

neatly

up

to

the

shoulders.

If

these

fit

tight,

they

need not be

pegged

for

brazing.

Fit the

top

stay

eyes,

into the

top

back

stays

in a

similar

way.

Cut

a small

notch

in the bottom

of

the

f-in.

hole

in

one

of

these

stay

eyes,

so

that a

small

peg

fitted

under

the head

of

the

bolt,

which

holds the

seat

pillar

tight,

may

engage

with

this

slot

and

so

prevent

the bolt

from

turning

while the

nut

is

being

tightened

or

undone.

Before

fitting up

the

fork

ends

and

stay

eyes,

or

cutting

the tubes

at

all,

see

that

the cranked

portion

of these

comes

in the

proper

position

to

allow

of

the

belt

rim

clearing

properly,

and

on the

left-hand side of

the

machine.

These four

joints

are

then

brazed

and

filed

up.

Setting

Rear

Fork

Ends.

The

fork

ends

should

now

be set on

the

wheel.

(The

wheels

should

be made

or

procured

before

starting

to

build the

frame.)

To

set the

fork

ends,

tighten

up

in

their

place

on

the

wheel

spindle

and

set

until

the

other

ends of

the

forks

are

the

proper

distance

apart,

to

correspond

with

the

D-section

ends

of

the

fork

crown,

and

at

an

equal

distance

from the

edge

of

the

whe-el rim.

It

is

better not

to

set

these* in their

place

on

the

spindle,

or

the

latter

may

get

bent with the strain

;

they

should

be

removed to the

vice to

be bent

to

the

required

angle.

Brazing

Tubes

to

Bottom

Bracket.

The two

short

pieces

of

If-in.

tube

may

now

be

fitted

to

the

bracket,

and

also

the down

tub,

after

thoroughly

cleaning

out

the

various

lugs

and

the

ends

of

the

tubes.

The

ends

of

the

If-in.

tube

that fit

into

the

bracket

should

be

hollowed

out,

to

allow

of

the

tubes

fitting

well

up

into

the

bracket. The

back

fork

crown is then

fitted

to

the other end

of

the

If-in.

tube.

Now

try

this


43/166

BUILDING

FRAME FROM

CASTINGS.

41

part

on

the

working drawing,

and see that all

the

measurements

and

the

angle

of

the down tube

are

correct.

Before

pegging

these

joints

and

braz-

ing up,

make

sure

of

the

following

points

:

The

down tube

must

be

at

right angles

to the

bore

of

the

bracket

;

test

this

with a steel

straightedge

on

the

trued-up

faces.

See that

the

back

fork

crown is

square

with

the

down

tube

;

test

this

by

placing

the-

straightedge

on

the

top

of the

D-sec-

tion ears

and

sighting

it from

the

back,

when

the

straightedge

should

appear

at

right

angles

to

the

down

tube. Some

blacklead mixed

with

oil

should

be

rubbed

into

the threaded

ends

of

the

bracket,

and

also

into

the

tapped

lubricator

holes,

to

pre-

vent

the brass

and borax

adhering

to

these

parts.

Fig.

33.

Engine

Plate Bolt.

These four

joints

will

require

careful

brazing,

and

a

good

blast

to

obtain sufficient

heat. The best

way

to

proceed

is to direct

the

blast on

to

the

heavy portion

of the front

lug

;

get

this

well

heated

up,

and

make

the

front

l|-in.

joint.

Now

shift

the

flame

on

to

the

root

of

the

l^-in.

lug,

and

braze

this

joint

;

then

on to

the

heavy

part

of the

rear

l|-in. lug,

and finish

this

joint.

It

will

be advisable

next to remove the

job

from

the hearth

and

thoroughly

brush

these

joints,

while

well

hot,

with

the

wire

brazing

brush.

The

joint

of

the

rear

If-in.

tube with the

back fork

crown

can then

be

finally

brazed.

Brazing

this

last

joint

will

scale

the

D

ends of

the

crown,

and

these

must therefore be

cleaned

up

again

before

fitting

the

back forks. Small air-holes

must

be


44/166

42

MOTOR

BICYCLE BUILDING

drilled on

the

inside of

these

back

forks

before

filing

up

and

brazing.

Other tubes

requiring

air-

holes

for

brazing

will

be

the back

stays,

lower

horizontal

tube,

and

front

forks

;

and

the

top

tube

and

bottom,

front

tube

as

well,

unless

the

ends

of

these

are

opened

out

into their

lugs.

When the

back

forks,

exactly

equal

in

length,

are

finally

fitted

to

the

crown,

remove

and

load

each tube

with brass

and

borax,

knock

the

joints

well

home,

and

peg

securely.

Fix

a

stay

or

strut

between

the

two

fork

ends,

so that

they

will

be

held

the

same distance

apart

as

they

will

be

when the

wheel

is in

position.

In

the

absence of

a

suitable

stay,

the hub

spindle

will

do,

the

cones and

nuts

being

used to

keep

the

fork ends

the

correct

dis-

tance

apart

and

the

faces

square with

each

other.

Shake

the

charge, placed

inside

the

tubes,

well

down

towards

the

joints,

and

braze

one

at

a

time,

with

the fork on its

side.

Fitting

Ball-head.

Fit

up

the

ball-head

tube

to

the

top

and

bottom

head

lugs,

the

top

tube

to the

top

head

lug,

and

the

bottom

front tube

to

the

bottom

head

lug,

and

peg

the

joints.

The

ends

of the tubes

should

be hollowed out to fit

up

against

the

head

tube.

Before

brazing,

see that

the

three

tubes are in

one

plane

;

to

test

this,

place

a

long

straightedge

across

the ends

of

the

top

and bottom

tubes,

and

sight

this with

the

ball-

head

tube.

Also

see

that

the ends

of

the

tubes

are

the

proper

distance

apart

to

drop

into

place

with

the seat

lug

and

front

engine

lug

on

the

draw-

ing.

While

these

joints

are

hot,

scrape

out

the

ends

of the ball-head

lugs,

where

the

ball

races

fit

;

this

will save a

lot

of

work

after,

if

any

brass

has stuck to these

parts.

Mark

off,

on

the

down

and

bottom

tubes,

the position

that

the

Ipwer

horizontal

tube

lugs

will

occupy,

and

clean

the

tubes

at

these

parts.

Slip

the

two

lugs

on

to

the

down

and bottom tubes

before

the

seat

lug

or

the

front

engine

lug

is

fitted

to

its tube.


45/166

BUILDING

FRAME FROM

CASTINGS.

43

Fitting

Front to Rear

Parts.

The seat

lug

can

now

be

fitted to

the

top

tube,

and the

lower

horizontal

tube

to

its

lugs,

and

the

front

and

rear

portions

of the

frame connected

together

by fitting

the

seat

lug

on

to

the

top

of the

down

tube.

In

fitting

this

front

portion

to

the

rear

part,

see

that all

the

tubes

lie

in one

plane

before

pegging

up.

To test

this,

place

a

long

straightedge

across

each

side

of

the ball-head

and down

tubes

;

the end

of

this should

fall

at

an

equal

distance

from each

fork-end face.

The

ball-head

tube

must also

be

perfectly parallel

with

the

down tube.

These

three

joints

may

now

be brazed

up.

The

top

tube

is

opened

out into the seat

lug

by punch-

ing

a

hole

through

the down

tube

inside the

seat

lug.

This

will

act

as

an

air

hole,

and

serve

as

a

means

of

feeding

a

charge

of brass and

borax

to

the

joint.

The

lower horizontal

tube

lug

joints

may

be

fed

by ramming

a

piece

of

paper

down the

tube,

about

the

centre,

before

fitting

up

;

a

charge

can then be

inserted

at

each end

of the

tube,

the

paper

keeping

them

apart.

Fitting

Top

Back Stays.

The

top

back

stays

may

now

be

fitted

and brazed

up.

Before

pegging

up

these

two

joints,

the

wheel

must

be

tried

in

place,

and

the

stays

so

fitted

that

the

rim of the

wheel

is

exactly

central between

them.

Fit

the

mud-guard

stay,

and braze in

place,

to

give

1^-in.

clearance between

the

mudguard

and the

tyre.

The

fitting

and

brazing

of the

engine

lugs

had

better

be

left

until

the

front forks

are built

and

the

engine

is

ready.

Fitting

Front

Forks.

Now

the front

forks

may

be

secured.

Fit and

braze the

steering

tube

to

the

fork crown

;

then

square

off

the

bottom ends

of

the

front

forks

and

clean

out

all

scale,

and

serve

the

lower ends

of

the

girder

tubes in the

same

way.

Fit

the

fork

ends to the

fork

blades,

set

in

the same manner as the rear

fork

ends

on

the front

wheel,

and braze

up

these two

joints.


46/166

44

MOTOR

BICYCLE

BUILDING.

Next

cut

off the

top

ends

of the

blades to

the

proper

length,

to

give

the

required

clearance to

the

tyre

under

the

fork

crown.

Clean

the

ends

of

the

blades

outside

sufficiently

far

down

to

allow

for the

girder

tube

stays,

then

slip

these

stays

on

over the

fork

blades,

load each

with

brass

and

borax,

and fit

into the

crown,

taking

care to

knock

them

well

home.

The

two blades

should be

of

exactly

the same

length,

and,

after

being

tested,

should

be

fixed

at

an

equal

angle

to

the

steering

tube when the ends

are

the

proper

distance

apart.

Fit the

wheel

in

the

forks,

and

see

that

the

rim

is

central

between

them,

and use

the

straightedge

to see

that

the

steering

tube is

true

with

the wheel

rim.

When

this is

all

as-

sured,

fix

the

wheel

spindle

or other stay

between

the fork

ends,

and

peg

and

braze

up

the

four

joints.

The

f-in.

holes

of the

girder

tube

stays

must

now

be cleaned

out,

the tubes where

they

fit

these,

and

the

inside

of

the

lower

ends,

to fit

on

the

front

lug

of

the

fork

ends.

The exact

length

of

these

two

girder

tubes

is

obtained

by

assembling

the

ball-head

with

balls

and

races

in

position.

It is

very important

that the

length

of

these

shall be

absolutely exact,

for

if

they

are

the

least

bit

too

long,

the ends would bottom

in

the holes

of

the

lugs

on

front

of

the

steering-tube

lug

before the

bearing

was

properly

adjusted.

The

tubes should

be

of

such

a

length

as

to

be

about

~

in.

off

the

bottom

of

the

holes,

when the

bearing

is

tightly

adjusted.

This

allows

for

subsequent

wear

and

adjustment

of

the head

bearings.

Of

course,

it-

is

understood that

the

tops

of

these

tubes are not

brazed

into

the

lugs,

but

are

a

good

tight sliding

fit

in

them.

When

the

proper

length

has been

obtained,

take

down

the

head and

braze the

four

joints

at

the crown

and

lower

ends.

It will

be as well

to

slip

the

steering

tube

lug

on

to

the

top

ends of

the

girder

tubes

while these

four

joints

are

being


47/166

BUILDING

FRAME

FROM CASTINGS.

45

brazed,

thus

ensuring

them

being

the exact

dis-

tance

apart

to

drop

afterwards

into their

places.

Before

filing

up

the

fork

joints*

try

the

front

wheel

again,

to see

if

any

part

has

sprung

or

given,

and

thus thrown

the

wheel

out

of

centre.

It

will,

of

course,

be

better

to correct this

now

than

to

wait

until after

the

joints

are

filed

up.

While

the wheel

is

in

the

fork,

both before and

after

brazing,

place

the

straightedge

across

the

front

of

the

fork

crown,

and

see

that

is is

parallel

with

the

wheel

spindle.

Should

the fork

be

on

the

twist,

this

can be rectified

by

holding

the

crown

in the vice and

inserting

a bar between

the

lower

end

of

the

fork

blades.

Handle-bar and

Seat

Pillar.

The

handle-bar

and seat

pillar

call

for no

special

mention,

ex-

cept

that

they

are

stronger

than

the

ordinary

cycle

type,

and that

the

handle-bar

is

wider and

longer,

as

already

mentioned. The

stem

of both

the

seat

pillar

and the handle-bar

should

be fitted

into

their

respective

tubes before the saw-cut is

made

down

them.

Fitting

Engine

Plates.

If

the

engine,

or

the

crank

case

of

the

engine,

is

now

available,

the

four

engine

plates

can

be fitted to

the crank case.

The

pair

on

the

pulley

side will

be

let

in

flush

with

the surface of

the crank

case,

so

as to

give

clearance to

the belt.

With the

engine

lugs

slipped

on

to

the

ends

of

the

bottom

down

tube

and

the

short

l--in.

tube,

the

proper

position

for

the

f-in.

holes

in the

engine

plates

and

the correct

position

of

the

engine

lugs

on

the

tubes

can

be

marked

off

to

bring

the

engine

square

and

per-

pendicular

in

the

frame.

The

two

lugs

should

be

pegged

on

the

tubes

while

the crank

case

and

plates

are

in

position

with

alj

bolts

in,

to ensure

their

coming

together

again

properly

when

brazed

up.

It

will

be

advisable to

blacklead

the inside

of

the

f-in.

holes

in

the

engine

lugs

before

brazing

to

prevent

them

scaling

or

getting

brass

on

them.


48/166


49/166

47

CHAPTER

IV.

MAKING

A

3i-H.P.

PETROL

MOTOR.

THE motor

to

be

described

in

this

chapter

will

develop

3i

h.p.,

and is suitable

for

the

frame

described

in

the

previous

chapters.

It

is

quite

powerful

enough

for use

with

a

trailer, side,

or

fore

car. With a

two-speed

gear,

it

may

also

be

used

for

a

tri-car.

This

is

not

an

experimental

engine,

but one

that has

been

made

and well

tried

over

some

thousands of

miles,

giving

every

satis-

faction.

It

is

of

original

design

and

simply

con-

structed

with

as few

parts

as

possible

(see

the

vertical

'section,

Fig.

34,

in

which

the

valve

springs

are

not

shown).

The

patterns

for all the

parts

are

finished,

and are

available

to

readers of

this

handbook

who would like

to

purchase

the

castings

instead

of

making

their

own

patterns,

so

that

an immediate

start

could

be

made.

The

cylinder

pattern

is

an

exceedingly

difficult one

for an amateur

to

make

;

in

fact,

it

is

the work of

a first-class

pattern-maker

to turn

out

a

good

working

pattern.

Fig.

35

is

a

section

of

the

cylinder

through

the

line

x x

in

Fig.

36,

which

is

a

plan

of

the

top.

Fig.

37

is

a

plan

of

the

bottom

or

open

end

of

the

cylinder.

Boring

Cylinder.

The

first and most im-

portant part

to

be taken

in

hand

is

the

cylinder.

The

boring

and

machining

of

this

calls

for

the

greatest

care

and

skill

to

obtain

really good

re-

sults.

The

cylinder,

etc.,

being

all

in

one cast-

ing,

increases the

difficulty

of

accurate

boring,

but

makes

a

much

more

satisfactory

job

when

finished.

Before

starting

the

boring operation,

the

casting

should

be

carefully

examined

for


50/166

MOTOR

BICYCLE

BUILDING.

Fig.

34. Vertical

Section

of

3|-h.p.

Petrol

Engine.


51/166

MAKING A

3A-H.P.

PETROL

MOTOR.

4


52/166

50

MOTOR

BICYCLE BUILDING.

carefully

chipped

'off.

The

open

end should

be

filed

level,

and a

piece

of hardwood

fixed across

the

open

end.

From

a centre

marjked

on

this

hardwood

the

size

of bore can be

scribed off

and

lightly

centre-dotted.

The bore

is

82

mm.,

or

approximately

^

T

in. under 3

in.

;

and the

stroke

is

3^

in.

In

outlining

the

bore,

it

is

advisable

to mark

just

outside

the exact

bore,

so that the

boring

will

not

completely

obliterate

the

marks.

There

is a

small boss on the

top

of the

cylinder;

this boss is

perfectly

central

with

the

cylinder

walls,

and is

placed

there

to

assist

in

setting

the

casting

true

for

boring,

and

to take

the centre

for

turning

up

the outside below the

radiators.

The boss should be

carefully

centred,

and

drilled

up

with

a

small

hole,

and

countersunk

to

the

same

angle

as

the lathe centres. Another

use for this

boss

is

to time the

valves,

by

passing

a

wire

down

a

hole

drilled

right through

and afterwards

stopped

up

with

a

small screw.

The

casting

may

be

strapped

to the

face

plate,

and

bored

up

with a tool

in

the slide-rest

or

strapped

down

to

the

saddle

and

bored with

a

stiff

boring

bar held in a

firm,

solid

chuck.

By

the first

method, cylinders may

sometimes

be

bored

accurately,

but the

chances

are

against

it.

The

latter method

will

be more

satisfactory.

A

good

stiff

boring

bar,

not

less

than

li in.

in

diameter

and

no

longer

than

absolutely

neces-

sary,

should

be used.

This should be fitted

with

a

flat cutter

made

from

l|-in.

by

j-in.

steel,

double

cutting,

the corners

being

rounded

off

and

the

cutting edges slightly

backed off.

Three

cutters

are

required,

a

roughing,

second,

and

finishing,

the last

being

only

slightly

rounded

on the

corners

and

the

cutting

edges

finely

finished

off

on

the

oil-

stone to

the size of

the bore

that

is,

82 mm.

The

cutter must

run

dead

true

in

the

lathe,

or the

bore

will

be

greater

than

the

width

of

the

cutter.

Three cuts should

be

sufficient,

the

finish-


53/166

MAKING A

3i-H.P. PETROL

MOTOR.

ol

ing

one

being

a mere

scrape.

During

the

finishing

cut

and

the one

before

it,

the

lathe

must

not

be

stopped

from

the

commencement

to

the

finish

of

the

cut.

The

job

may

be done

with one

cutter,

one

end

only

cutting,

and the cutter

adjusted

farther

out

for

each

cut;

but

it

should be

freshly

sharpened

for the

finishing

cut. A

single-ended

cutter

is

more liable

to

spring

and follow

in-

equalities

in the

casting

than

a

double-ended

one,

and

for

this

reason

at

least

one

extra

cut

should be

employed

in

the

operation.

The

casting

must

be

very carefully

set,

and

Fig.

37.

Plan

of

Bottom or

Open

End

of

Cylinder.

bolted

down with

good

broad

straps,

one

strap

coming

across the thick

part

of the

valve

cham-

ber and

the other

across

the

flange

at

the bottom.

Secured in this

manner the

casting

is less

liable

to

be

sprung

out

of

shape.

The

cylinder

walls

being

only

^\

in. thick

(finished),

no

allowance

can

be made for

any

inaccuracy

in

setting.

The

small

lug

on

top

of

the

cylinder

will

here be found

useful,

as the

back

centre

of

the

lathe can

be

brought

up

close

to

the

casting

and

used

to

test

the

accuracy

of

this end

;

the

open end,

of

course,

can

be

more

easily

set

by

the

cutter

edges.

The

cutter

slot

in

the

boring

bar

should

be

within

-4

in.

of

the

end,

to avoid

any

risk

of

the

end

of

the

bar

coming

in

contact

with

the

cylinder


54/166

62

MOTOR BICYCLE BUILDING.

end

and thus

shifting

the

setting;

this

would be

disastrous

in

the

finishing

cut

or the

one before

it.

It will

be

noticed

that the last

f

in.

of

tne

cylinder

is

shown counter-bored.

It will

not

be

necessary

to

bore

this

part

if

the

casting

is

accurately

set,

as the

casting

is

cored

out at

this

part

y

1

^

in.

larger

than

the

finished bore.

Machining

Chamfer

at

Mouth

of Cylinder.

At

this

setting,

after

the

bore

is

finished,

the

chamfer

at

the

mouth

of

the

cylinder

should be

machined.

This can

be

done

with a

separate

cutter,

or a

corner of

the back

portion

of on-e used

for

boring

may

be filed

to

the

necessary

shape.

This

chamfer

is

necessary

for

the

easy

insertion

of

the

piston

when

the-

rings

are

in

position.

The

extreme

end

may

also

be

trued

up

with

the

cutter

at this

setting.

This

should be done to

allow

of

the

under

part

of

the

flange

being

-^

in.

from the

end

and

the

cylinder

6|

in.

deep.

To machine the

valve

chamber,

the

casting

should

be

firmly

bolted

down

to

a

perfectly

true

face

plate,

2|

in.

out

of

the

centre,

to

get

the

opening

true.

As

the

sur-

face

in

contact

with

the

face-

plate

is

so

small,

the

casting

is

liable

to

shift

during machining

unless

it

is

very

firmly

bolted

down.

A

sheet

of brown

paper

placed

between

the

face

plate

and the

mouth

of

the

casting

will

greatly

assist

in

keeping

it

from

shifting.

Valve

Seating,

Opening,

etc.

When

set

true,

bore

out

and

screw

the

exhaust-valve

guide

holes

A

(Fig.

35)

to

f-in.

whitworth. With

a hook

tool,

face the

under

side

of

this

hole

for

the collar

on

the

guide

to bed

true

against

;

this collar

will be

1

T

V

in.

in

diameter.

The

seating

for

the

exhaust

valve

will

be

bored

out

If

in.,

the

upper

side

being

chamfered

as

shown

and

the

top

trued

up.

The

opening

for

the inlet

valve

is

bored out

lj in.,

and

chamfered

the

same

as

the exhaust

opening

;

\

in.

above this

bore

out

If

in.

;

the

remaining portion

B

(|

in.)

is

bored

1

T

^

in.

bare,

and

screwed 20


55/166

MAKING

A

3A-II.P.

PETROL

MOTOR. 53

threads

to

the

inch,

which will

make

it

If

in.

at the

bottom

of

the

thread.

Face

off

the

top

of

the

opening

true

to

the

dimensions

given.

Turning

up

Outside

of

Cylinder.

To

turn

up

the outside

of

the

cylinder

below the

radiators,

the

casting

should

be

run on

the

centres. For

this,

a

large

centre

to fit

the

back

poppet

of

the

lathe

must

be

made,

or

the

mouth

of

the

cylinder

may

be bridged

with

a

stout

piece

of

iron

or

steel

carefully

fitted to

the

bore

and

centred

true. The

outside between

the

lower

radiator

and

the

top

of

the

flange

is turned to

3

T

7

^in.,

the

flange

being

left

$

in.

thick,

and

the

shoulder

3j

in.

in

diameter

by

-j^

in.

deep

;

this

shoulder should be

left

with a

very

slight

taper

on

it,

so

that

it

may

fit

tight

into

the

opening

in the

top

of

the

crank

case.

Opening for

Exhaust

Pipe,

etc.

The

opening

for

the exhaust

pipe,

which

is

indicated

by

the

dotted

circle

c

(Fig.

1)

in

the

centre

of

the

valve

chamber,

must

now

be-

drilled

and

tapped.

This

is

lj

in.

by

26

threads,

and is best

done

on the

drilling

machine,

using

a

suitable

tap

to

form the

thread,

as

it

is rather

awkward

to chuck or

hold

in

the

lathe.

The

sparking-plug

hole

D

is drilled

and

tapped

|~J

in.

by

17

threads,

and is faced

on

the

outer

surface.

Flange

on

Cylinder

Bottom. The

flange

on

the

cylinder

bottom

is left the

full

size

at

present,

being

filed

off

flush

with

the flange

on

the

top

of

the

crank case after

the

two

parts

are

fitted

to-

gether.

Holes

for

Holding-down

Bolts.

The

four

f-in.

holes for

the

holding-down

bolts,

shown

in

the

plan

of

the

bottom

end at

Fig.

3,

should

be

drilled

in

such

a

position

as

to

Leave

an

equal

amount of

metal

round

the

corresponding

holes

in

the

crank

case,

but

keeping

the

holes

sufficiently

far from

the

outer

face of the

cylinder

to enable

the corners

of

the

bolt

heads

to clear

properly.

Piston. The

piston

casting

should now

be


56/166

54

MOTOR

BJCYCLE

BUILDING.

trimmed

up by

filing

or

carefully

chipping

off

all

rough projections

left

from

the

foundry.

The

cast-

ing

should be chucked

by

the

projection

left

on

the

end

of

the

casting,

in

a

3-jaw

or

4-jaw chuck,

and

should

not

be

shifted

until

all

the

turned

work

is

finished.

In

setting

the

casting,

true

up

from

the

inside,

for

unless the inside is

true the

piston

will

be

very

thin

on

one

side

when

finished,

as

the

walls

will

be

rather

light

in

parts.

Turn

up

the

outside

perfectly

parallel

from end

to

end,

82

mm.

in

diameter;

it should

be

a

fairly

easy

fit

in

the

cylinder

at this

stage.

Turn

as

near

the

size

as

possible

with

a

light

finishing

cut,

and

smooth off

to

the

final

fitting

with

a dead smooth file. True

up

the

open

end,

and

with

a

good

sharp

parting

tool

cut

down

the

head

to

the

projection by

which

the

casting

is

held,

leaving

it

3j

in.

long

from end

to

end.

Ring

Grooves in Piston.

The

ring

grooves

may

now

be

put

in

;

these

are

y^-

in.

wide

by |

in.

deep,

and

are

g

in.

apart,

the first or

top

one

starting

J

in.

from

the

end.

The

tool

with

which

these'

are cut

must

be

carefully

made

and

set,

so

as

to

leave the sides

perfectly square

and

the

corners

sharp.

A

tool

made as a

parting

tool,

jusb

yV

i

n

-

wide,

with

the sides

slightly

backed

off,

will

do

the

job

at

one

cut,

and ensure them

being

all the same width

;

but

unless

the

lathe

is

a

good

solid

tool,

free from

spring,

the

yV^

n

-

cu

^

may

be

too

much for

it

and

set

up

chattering.

In this

case,

a

narrower

tool

must

be

made,

not

more

than

g

in.

wide.

Whichever

way

the

job

is

done,

the sides of

the

grooves

must

be

perfectly

parallel

and

square.

A

small

sheet-metal

template

should

be

filed

out for

the

purpose

of

testing

them

for

depth

and

width.

Gudfjeon-pin

Hole. At a distance

of

lj

in.

from

the

top

end,

scribe a

line

round

the

piston

with

a

sharp-pointed

tool

held in

the

slide-rest

motorbicycle building

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